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Cell Biology Exam
Chapters 7, 8, 9, 15 and 16
| Question | Answer |
|---|---|
| Chapter 7 | |
| How are Defined tissues formed? | When cells interact with extracellular material. |
| What are 2 defined tissues? | Epithelial Tissues and Connective tissues |
| * What is the Glycocalyx formed from? | Carbohydrate projections from the plasma membrane |
| * What does the Glycocalyx do? | It mediates cell-to-cell and cell-substratum interactions |
| * Where is the Extracellular Matrix (ECM) network found? | beyond the plasma membrane. |
| What type of network is the Extracellular Matrix (ECM)? | an organized network |
| What type of role does the Extracellular Matrix (ECM) play? | a regulatory role in determining shape and activities of the cell. |
| The Extracellular Matrix (ECM) includes what ? | The Interstitial Matrix and the Basement Membrane (Basal Lamina). |
| What is the Basement Membrane? | a continuous sheet that underlies the epithelial tissue and surrounds blood vessels. |
| What does the Basement Membrane do? | -Helps maintain cell attachment -Serves as a substratum for cell migration -Forms a barrier to macromolecules |
| What is Collagen and where is it found? | Its a fibrous glycoprotein found only in the ECM |
| What is Corneal Stroma? | Layers of collagen fibrils of uniform diameter |
| Do all Collagens form fibrils? | No, some collagen (Collagen IV) is non fibrillar. |
| What is a Proteoglycan? | Protein polysaccharide complex with a core protein attached to Glycosaminoglycans (GAG). |
| What do negatively charged GAGs do? | attract lots of cations, which in turn attract water formin a porous, hydrated gel |
| The Proteoglycans are cross linked into a large matrix by what? | Hyaluronic acid |
| Why does the proteglycans resist crushing forces? | Because they bind huge numbers of cations which binds large numbers of water molecules and forms a hydrated cell that fills the extracellular space like a packing material |
| Whats does the Proteoglycans do? | -provide binding site for growth hormones in order to protect from proteases -regulate diffusion of small signalingl molecules in the developing embryo |
| What does the proteoglycans contain? | the cartilage matrix contains 30 keratin sulfate and 100 chondroitin sulfate chains |
| What is Fibronectin (Fn)? | a linear array of distinct polypeptides giving it a modular structure |
| How much is 1 polypeptide in comparison to Fn modules? | 30 Fn modules |
| What does the Fn modules do? | -more binding sites for other components of the ECM (for collagens, proteoglycans, etc) -guides migrating cells during embryogenesis |
| What can Fibronectin (Fn) be considered as? | "building blocks" |
| What are Laminins? | extracellular glycoproteins that consist of 3 polyptptide chains linked by disulfide bonds |
| How many different types of Laminins are there? | 15 have been identified |
| What does the Laminins affect? | a cells migration, growth and differentiation pattern |
| Laminins play a a critical role in the migration of what cells? | Primordial germ cells |
| The Laminins molecules and IV Collagen molecules form what? | seperate but interconnected networks in the basement membrane that helps give it flexibility and strength |
| What are 3 dynamic properties of the ECM? | -it can be stretched during tension -its not static, has constant remodeling by degradation and reconstruction -The ECM molecues are degraded by Matrix Metalloproteinases (MMPs) |
| What does Matrix Metalloproteinases (MMPs) cause? | diseased states in the ECM due to possible involvement in tissue remodeling, migration, wound healing and formation of blood vessels |
| What are Integrins? | a family of membrane proteins composed of heterodimers with a and B subunits. |
| What are the two major roles Integrins have? | -integration of extracellular and intracellular environments -adhesion of cells to their substratum or even to other cells |
| What is Inside-out Signaling? | when talin bonds to the cytoplasmic tails and separates the a chains from the B chains which allows Integrin to bind extracellular matrix ligands |
| What happens when Integrins and Ligands link together? | It mediates adhesion between cells and their environments |
| What facilitates binding of proteins to Integrins? | Tripeptide RGD |
| Fibrinogen binds to Integrin for what purpose? | to glue platelets together |
| What happens when platelets adhere to one another through fibrinogen bridges that bind to the platelet-integrin? | Blood clots form |
| What is a competitive inhibitor to Fibrinogen/Integrin interaction? | RGD peptide |
| What do Integrins do? | make the connection between teh ECM and the cytoskeleton |
| What is Focal adhesion? | sites where cells adhere to their substratum and send signals to the cells interior -are also implicated in cell locomotion |
| What is Hemidesmosomes? | it is a cell-substratum adhesion site that connects the extracellular matrix to the keratin cytoskeleton. |
| What do cells have in order to maintain organization? | Surface-recognition sites |
| What are Selectins? | integral membrane families of glycoproteins that bind to sugars on the surface of cells |
| What are the 3 types of Selectin? | E-selectin -on endothelial cells P-selectin -on platelets and endothelial cells L-selectin -on white blood cells |
| What is Inflammation? | A response to infection or injury but it can be triggered inappropriately |
| What are 3 Inflammatory responses? | -Recruitment of Leukocytes to the site of injury -Neutrophils attach to E and P selectins -Neutrophils start to "roll" along wall of vessel |
| What are the 3 movements of the neutrophils during inflammation? | -Platelet activating factor (PAF) is displayed when neutrophils interact with the inflamation site -PAF sends a signal to increase binding activity of integrins Activated integrins stop the neutrophils from rolling and adhere them to the wall of vessel |
| Metastasis is when what happens? | a tumor spreads to other parts of the body |
| What are the cell adhesion properties of Metastatic cells? | -less adhesive -able to penetrate several barriers -able to invade normal tissues |
| What is an Immunoglobin Superfamily (IgSF) | a large group of cell surface and soluble proteins that are involved in the recognition, binding or adhesion processes of cells. |
| What do most IgSF do? | mediate interactions of lymphocytes with cells required or in the immune responses. |
| What are examples of mediated adhesion between non-immune cells? | VCAM (vascular cell-adhesion molecule) NCAM (Neural cell adhesion molecule) L1 (neural development) |
| What are Cadherins? | Glycoproteins that mediate Ca 2+-dependent cell-cell adhesion. |
| What do Cadherins do? | Join cells of similar types to one another by preferential binding to the catherin present at the surface of the neighboring cell |
| What are the 3 types of Cadherin? | E-cadherin (epithelial) N-cadherin (neural) P-cadherin (placental) |
| What other 2 things Cadherins do? | -transmitting signals from the ECM to the Cytoplasm -Mediate changes in the adhesive contacts in embryonic development by forming Epithelial-Mesenchymal Transition (EMT). |
| What do Adherens junctions do? | form "belts" near apical surface called junctional complex |
| B-catenin has been implicated as key element in signaling what? | Pathways leading the cell surface to the cells nucleus |
| What are Desmosomes? | disk-shaped adhesive junctions between cells |
| What do Desmosomes contain? | Cadherins that link the two cells across a narrow gap |
| What are the 2 different domain structures of Desmosomes Cadherins? | -Desmogleins -Desmocollins |
| What is Transmembrane Signaling? | The transfer of information across a plasma membrane |
| What 2 things can transmit signals from the extracellular environment to the cytoplasm? | Integrins and Cadherins |
| What are Tight Junctions (TJs)? | Specialized contacts between epithelial cells |
| Where are Tight Junctions (TJs) located? | at the very apical end of the junctional complex between adjacent cells |
| What does the Tight Junctions (TJs) do? | Serves as a barrier to free diffusion of water and solutes from the extracellular compartment |
| What are Occludins? | proteins found in the Tight Junctions (TJs) |
| What is the newly discovered type of communication called? | Tunneling nanotubes |
| Where was Tunneling nanotubes observed? | growing in culture |
| What can the Tunneling nanotubes do? | transmit viral particles and prions |
| What are Plasmodesmata? | cytoplasmic channels passing through cells walls of adjacent plant cells |
| What is the central structure of the Plasmodesmata? | Desmotubule |
| What does the Plasmodesmata do? | serves as a sites of cell-cell communication |
| What do Cell Walls do? | provide plants protection against mechanical abrasion, pathogens, and osmotic stress |
| What is the fibruous component of the Cell wall? | Cellulose |
| Cellulose is organized into what form and what does it do? | into Microfibrils which provide rigidity to the Cell wall |
| What 3 things does the matrix of the Cell wall contain? | Hemicellulose, Pectin, and Proteins |
| Between the plasma membrane of a newly formed daughter cell, what does the Cell wall arise as? | A cell plate |
| When is Glucose added to Cellulose synthase? | to the end of the growin cellulose molecule |
| Where are the materials of the cells matrix synthesized? | in the cytoplasm and carried to the cell surface in secretory vesicles. |
| Chapter 8 | |
| What organelles does the Endomembrane system include? | Endoplasmic reticulum, Golgi complex, Endosomes, Lysosomes and Vacuoles |
| Organelles of the Endomemembrane system are a part of an integrated network that does what? | Shuttles materials back and forth |
| How are materials shuttled between organelles? | Membrane bound Transport Vesicles |
| What are 2 pathways through the cytoplasm? | Biosynthetic Pathway Secretory Pathway |
| What does the Biosynthetic pathway do? | It synthesizes, modifies and transports proteins |
| What happens in the Secretory pathway? | Proteins are discharged (secreted) from the cell. |
| What are the 2 types of secretion in the Secretory pathway? | Constitutive secretion -in a continuous fashion Regulated secretion - in response to a stimulus |
| During regulated secretion, the materials to be secreted are stored where? | Membrane-bound Secretory granules |
| What is Autoradiography? | A method to visualize biochemical processes using radiolabeled materials exposed to a photographic film |
| What can Autoradiography be used for? | The determination of where secretory proteins are synthesized, by using labeled amino acids |
| What is the Green fluorescent protein (GFP)? | A small protein isolated from jellyfish which emits green fluorescent light |
| Why are Green fluorescent proteins (GFP) important? | -Allows to observe the protein synthesis in the cell -fusing it to viral genes shows protein traffic due to large production of proteins |
| What is Sub-cellular fractionation? | The use of different techniques to homogenize celles and isolate some organelles which can then be seperated from one another |
| What is Homogenization? | it is the state at which you bring biological material and make it inot equal composition. |
| What are Microsomes? | They are vesicle like artifacts that were re-formed from pieces of the Endoplasmic reticulum during Homogenization. |
| What are Cell-free systems? | A system that does not contain whole cells and have provided people with informtion about the roles of proteins involved in membrane trafficking |
| Why do we study Mutants? | They provide insights about the function of normal gene products |
| What is RNA interference? | A process in which cells produce small RNAs (siRNAs) that bind to specific mRNAs and inhibit the translation of these into proteins. |
| What is the Endoplasmic Reticulum comprised of? | A netwrok of membranes that penetrates much of the cytoplasm |
| What are the 2 subcompartments of the Endoplasmic Reticulum? | Rough Endoplasmic Reticulum (RER) Smooth Endoplasmic Reticulum (SER) |
| What is the internal space of the Endoplasmic Reticulum (ER) called? | The luminal or the cisternal space |
| What is the Rough Endoplasmic Reticulum (RER) composed of? | A network of flattened sacs called Cistenae |
| What are the 3 mani functions of the Smooth Endoplasmic Reticulum (SER)? | -Synthesis of steroid hormones in endocrine cells -Detoxification in the liver of various organic compounds -Sequestration of calcium ion from citoplasm of muscle cells |
| What is a Leydig Cell? | An extensive SER where steroid hormones are synthesized |
| What are the Functions of the Rough Endoplasmic Reticulum (RER)? | -Tranpsort of proteins made by ribosomes |
| What is the difference between the synthesis of proteins on Membrane-bound versus "free" Ribosomes? | -1/3 polypeptides encoded by human genome are synthesized on ribosomes of RER. (includes 3 polyp) -on free ribosomes (6 polypeptides) |
| What is a Signal sequence and where is it found? | Its a short peptide found at the N-terminus of, majority, newly synthesized proteins that are destined towards the secretory pathway |
| How do Polypeptides move into the Endoplasmic Reticulum (ER)? | In the Cisternal space through a protein-lined pore. |
| What does Messenger RNA (mRNA) bind to? | Free ribosomes on the cytosol |
| What does a Signal Recognition Particle (SRP) do? | Recognizes the secretory proteins synthesized on the membrane-bound ribosomes. |
| What are the two sequential interactions for binding to the Endoplasmic Reticulum (ER)? | SRP must interact with an SRP receptor Ribosome must interact with the Translocon (a protein lined channel) |
| What happens to the ER after binding of the SRP-ribosome-nascent peptide chain complex occurs? | SRP is released but GTP-binding proteins (G proteins) are required |
| What happens when the newly synthesized proteins enter the ER? | Once it enters the RER lumen, the signal sequence is cleaved by a signal peptidase |
| How are Carbohydrates added to the RER? | By the enzyme oligosaccharyltransferase |
| What do Integral proteins contain that interfer with transfer into the RER lumen? | Hydrophobic trans-membrane segments |
| What are 4 steps of membrane Biosynthesis in the ER? | -Membranes arise from other pre-existing membranes -lipids are inserted into existing membranes -as membranes move from compartments its proteins and lipids are modified -membrane asymetry is eastablished initially and maintained during trafficking |
| What does Flippases do? | Inserts newly synthesized phospholipids into half of bilayer facing the cytosol and then flips them to the opposite leaflet |
| What are the 3 contributing factors to the variation of organelle lipid contribution? | -Specific organelle enzymes for lipid conversion -Inclusion/exlusion process during vesicle formation -Lipid-Transfer protein bind and transfer lipids without the use of vesicle transport |
| What happens to additional sugar during the Glycosylation in the RER? | They are catalyzed by Glycosyltransferases |
| What happens to the core segment of each carbohydrate chain? | It is put together on a lipid carrier (Dolichol Phosphate) and then transferred to a polypeptide |
| What happens to the core carbohydrate once it is transferred nto the ER lumen? | It is modified by oligosaccharyltransfer as the polypeptide. |
| What happens to the glycoprotein during Glycosylation in the RER? | I goes through a system of quality control to determine its fitness for a specific compartment |
| What happens if a protein does not correctly fold? | It is translocated to the cytosol and destroyed. |
| Where do the misfolded proteins get destroyed? | They get transported to the cytosol where they are destroyed in proteasomes |
| What is the process of destruction of misfolded proteins called? | ER-associated degradation (ERAD). |
| The accumulation of misfolded proteins triggers what? | Unfolded protein responses (UPR). |
| How are the misfolded proteins sensed? | The sensors in the ER are inactive by the chaperone BiP, but if a misfolded are accumulated the BiP can not inhibit the sensors |
| What are the 2 things that help the First Step in Vesicular Transport? | -RER have specialized exit sites where transport vesicles are formed -Transport vesicles fuse with one another and form the ERGIC (Endoplasmic reticulum Golgi intermediate compartment) toward the Golgi complex |
| What is the Golgi Complex comprised of? | A stack of flattened Cisternae |
| What is the cis Golgi Networks (CGN) function? | To sort out proteins for the ER or the next Golgi station |
| What is the trans Golgi Networks (TGN) function? | Sorting proteins to wither the membrane or the various intracellular destinations |
| What happens during the Glycosylation in the Golgi Complex? | -The carbohydrates are assembled |
| What does Vesicular Transport Model do? | Shuttles cargo from the CGN to the TGN in the vesicles |
| What happens in the Cisternal Maturation Model? | Each cistern "matures" and moves to the cis face to the trans face |
| What happens in the Current Model? | It does vesicle retrogade transport. |
| How are materials carried between compartments? | Coated vesicles |
| What are the 2 functions protein coats have? | -cause the membrane to curve and form a vesicle -select the components to be carried by vesicle |
| What are the 3 types of coated vesicles? | -COPII-coated vesicles -COPI-coated vesicles -Clathrin-coated vesicles |
| What does the COPII-coated vesicles do? | Move materials fromt he ER forward to the ERGIC and Golgi complex. |
| What does the COPI-coated vesicles do? | Move materials fromt he ERGIC and Golgi backward to the ER, or from the trans Golgi to the the cis Golgi cisternae |
| What does the Clathrin-coated vesicles do? | Move materials from the TGN to endosomes, lysosomes, and plant vacuoles. |
| In the COPII-coated vesicle what is the small G protein called and what does it do? | Sar1 and it plays a regulatory tole in the assembly of vesicles |
| How is disassebly triggered? | By hydrolysis of GTP which produces Sar1-GDP |
| What are 2 ways proteins are maintained in COPI-Coated vesicles? | Retention- of resident molecules that are excluded from transport vesicles Retrieval- of escaped molecules back to the compartments wher they reside |
| How does the sorting and transport process of Lysosomal enzymes work? | -Lysosomal proteins are tagged with phosphorylated mannose residues -Tagged lysosomal enzymes are recognized and captured by mannose 6-phosphate receptors (MPRs). |
| What do the coats of the Clathrin-coated vesicles contain? | -Outer lattice composed of Clathrin -Inner shell composed or protein adaptors |
| What are the Rab proteins on vesicles and target membrane involved in? | recruting tethering proteins that mediata initial contact between the two membranes. |
| What are the 2 docking vesicles to the target compartments? | -v-SNAREs (incorporated into vesicles) -t-SNAREs (located in target) |
| What is the Docking Stage? | when the v-SNAREs in the vesicle membrane interacts with the t-SNAREs |
| What are the 3 models of interactions between the v-SNAREs and the t-SNAREs? | -Synaptic vesicle docks to plasma membrane due to formation of four-stranded protein bundles -Transition state in the fusion of the 2 membranes -Transmembrane helices are now present and a fusion pore is opened between vesicle and target membrane |
| What is Exocytosis? | The discharge of a secretory vesicle or granule after fusionwith plasma membrane |
| How is Exocytosis triggered? | by an increase in Ca+2 |
| What does the contact between vesicle and plasma membrane lead to? | The formation of fusion pores |
| What do Lysosomes contain? | Acid hydrolases that can digest every type of biological molecule |
| What is the key role that lysosomes play? | organelle turnover |
| What is autophagy? | when an organell is surrounded by a double membrane and a structure called and Autophagosome is produced |
| What happens when the Autophagosome fuses with a lysosome? | They produce an Autophagolysosome |
| How are Lysosomal storage disorders formed? | The absense of specific lysosomal enzymes thus allowing undigested material to accumulate. |
| How is the Tay-Sachs disorder formed? | From a deficiency in an enzyme responsible for degrading gangliosides |
| What are 2 different types of treatments for lysosomal storage disease? | -Enzyme replacement therapy -Substrate reduction therapy |
| What is a vacuole? | a membrane bound, fluid-filled compartment |
| What is the vacuole membrane and what does it do? | Tonoplast and it contains an active transport system to keep a high concentration of ions so that water enters by osmosis |
| What is Endocytosis? | The uptake of cell surface receptors and bound extracellular ligands |
| What is Phagocytosis? | uptake of particular matter |
| What are the 2 categories that Endocytosis can be divided into? | Pinocytosis (nonspecific uptake of extracellular fluids Receptor-mediated endocytosis (RME) is the uptake of specific extracellular ligands following their binding receptors |
| What happens to substances that enter the cell through Clathrin-mediated RME? | They become bound to Coated pits on the plasma membrane |
| How is Triskelion formed? | In Clathrin that contains 3 heavy and 3 light chains |
| What is Dynamin? | a G protein thats required for the release in Clathrin-coated vesicles from the membrane where it formed |
| What does Dynamin promote? | A GTP-mediated fission of the coated pit from the plasma membrane followed by disassembly of the dynamin ring |
| Where are AP2 adpators normally found? | in the cytosol in a locked conformation |
| What happens in the Endocytic Pathway after internalization? | vesicle-bound materials are trasported in vesicles and tubules known as endosomes. |
| Where are early and late endosomes found? | Early- located near the periphery of the cell Late- near the nucleus (also known as Multivesicular bodies or MVBs) |
| What are Low-density lipoproteins (LDLs)? | A complex of cholesterol and proteins |
| Where are the LDL receptors transported? | the plasma membrane to be bound to a coated pit |
| What happens to the LDLs? | They're taken by RME and taken to the lysosomes, where they release cholesterol o be used by the cells |
| What do High-density lipoproteins (HDLs) do? | transport cholesterol from the tissues to the liver for excretion |
| What is the difference between LDLs and HDLs? | HDLs associated with low cholesterol LDLs associated with high cholesterol |
| What is Phagocytosis? | The process of engulfment. |
| What happens during Phagocytosis? | The plasma membrane engulfs a particle and turns it into a Phagosome The Phagosome fuses with a lysosome =Phagolysosome |
| How does the Phagocytosis commence? | By the actin containing microfillaments |
| The uptake of proteins into peroxisomes is mediated by what? | Peroxisomal Targeting Signal (PTS) |
| For the Mitochondria to uptake proteins, what must occur? | -proteins must be unfolded -They must go through two types of import complexes: TOM Complex or TIM Complex TIM Complex has two major complexes TIM22, TIM23 |
| During the uptake of the proteins into the mitochondria what happens? | -movement into mattrix is voltage dependent -Chaperones are involved in unfolding and later refolding the protiens |
| During uptake of proteins into the chlorplast, where are most proteins imported from? | the cytosol |
| The outer and inner envelope membranes contain what 2 translocation complexes that help the importationof proteins? | Toc and Tic |
| Where are the proteins folded and unfolded? | unfolded in the cytosol and refolded in the chloroplast |
| What did Brown and Goldsteing demonstrate? | Those affected with FH (Familial Cholesterolemia) had a defect in RME of LDL |
| Chapter 9 | |
| What is the cytoskeleton | A network of filamentous structures (i.e microtubules, microfilaments, and intermediate filaments) |
| What are some of the cytockeletons roles? | -structural support, maintaining cell shape -internal framework for organizing organells within the cell -directs cellular locomotion and movements of materials within the cell |
| What is Live-cell fluorecence imaging used for? | to locate fluorescent labeled target proteins in order to reveal the location of a protein present in very low concentrations |
| Why is In Vitro Single-molecule Assays used? | make it possible to detect the activity of an individual protein molecule in real time |
| Describe the structure of a microtubule? | hollow cylindrical structures |
| What are Protofilaments? | microtubules in a set of globular proteins arranged in longitudinal rows |
| What are Microtubule-Associated Proteins (MAPs) comprised of? | Heterogeneous group of proteins |
| Where can Microtubule-Associated Proteins (MAPs) be found and why? | attached to the surface of the microtubules in order to increase their stability and promote their assembly |
| What do Microtubules do? | -The distribution of the microtubules determines the shape of the cell -maintain the internal organization of cells -lay a role in axonial growth during embryogenesis |
| What do Microtubules do as agents of Intracellular Motility? | -Facilitate movement of vesicles between compartments -Axonal transport |
| How do microtubules help n Axonal transport? | -with the movement of neurotransmitters across the cell -the movement away from the cell body (anterograde) and toward the cell body -mediate tracks for a variety of motor proteins |
| What is required for Microtubule assembly? | GTP |
| What does the hydrolysis of GTP lead to? | the replacement of bound GDP by new GTP to recharge the tubulin dimer |
| What proteins regulate the rate of growth and shrinkage? | proteins called +TIPS |
| What is the structure of cilia and flagella? | there hair-like motile organelles |
| What type of pattern does flagella exhibit? | beating waveform pattern |
| What is the central core of the flagella and cilia called? | Axoneme |
| What is the basic structure of the axoneme? | a center sheath connected to the tubules of peripheral doublets by Radial Spokes |
| What are the peripheral doublets interconnected to? | to one another by an Interdoublet Bridge |
| What is Intraflagellar Transport (IFT)? | the process responsible for assembling and maintaining flagella. |
| What does IFT depend on? | the activity of both plus end- and minus end-directed microtubules |
| What is requiredfor ATP hydrolysis and why? | Ciliary (axonemal) dynein because it supplies energy for locomotion |
| Each Dynein is composed of what and why? | heavy chain thats composed of a long stem, wheel-shaped head and a stalk. the head serves as the basic driving force for ciliary and flagella motion |
| What generates forces for ciliary and flagella movement? | Swingnin cross-bridges |
| What tubules bind together in order to slide past each other? | A tubule binds to B tubule in a conformation change |
| What is Situs Inversus and how is it caused? | a syndrome in which the left-right body symmetry is reversed. Mutations in the gene encoding ciliary proteins |
| What is Intermediate filaments (IFs)? | a heterogenneous grop of proteins, divided into five major classes. |
| What are the classes 1-4 used for? | the construction of filaments |
| What is the class 5 used for? | present in the inner lining of the nucleus |
| What is the assembly of the Intermediate Filament (IF)? | a rod-like tetramer forme by 2 antiparaller dimers. Both the tetramers and the IF lack polarity |
| What controls the assembly and disassembly of the IFs? | Phosphorylation and dephosphorylation |
| What are the 2 types and functions of IFs? | -IFs carrying keratin form a protective barrier of the skin -IFs include Neurofilaments, which is the major component of the network supporting neurons |
| What are microfilaments composed of? | Actin and are involved in cell motility |
| What does the Actin assembly and disassembly in vitro depend upon? | the concentration of actin monomers |
| Actin subunits are added where and removed where? | added to plus end and removed from minus end |
| What are 3 dynamics of polymerization that can be altered pharmacologically? | -Cytochalasin D: blocks + of actin filaments -Phalloidin: binds to intact filaments, prevents turnover -Latrunculin: binds free monomers and prevents incorporations |
| What 2 groups can Myosin be divided into? | -Conventional (type 2) Myosins -Unconventional Myosins |
| What does the Conventional (type 2) Myosins do? | generates force into the muscles and some no muscle cells |
| What does Unconventional Myosins have? | a single head and are unable to assembly into filaments |
| What is Myosin V involved in? | organelle transport |
| What can Myosin motors, such as Myosin V, do? | transport their cargo over microfilaments, including those present in the peripheral regions of the cell |
| What are Hair cells? | hair-like stereocilia that project from the apical surface of the cell into the fluid-filled cavity of the inner ear |
| What does the displacement of the stereocilia lead to? | the generation of nerve impulses that we perceive as sound |
| What is a Skeletal Mucsle Fiber? | A multinucleate cell as a result of fusion of myoblasts in the embryo |
| What does each Muscle fiber contain? | hundreds of cylindrical strands called Myofibrils |
| What does each Myofibrils consist of? | a repeating array of Sarcomeres |
| Each Sarcomeres have what? | a banding pattern that gives muscle fiber a striated appearance |
| What are the 4 different sliding filament models of muscle contraction? | -Skeletal muscle works by shortening fibers -A bands remain constant in lengths -H and I bands decrease in width -Z lines on both ends of sarcomers move inwards |
| What 3 things do thin filaments contain? | Actin Tropomyosin Troponin |
| Where does Tropomyosin occupy? | the gap between 2 actin molecules |
| What are Titin filaments? | elastic filaments that prevent the sarcomerefrom being pulled apart by muscle streching |
| What do Nebulin molecules do? | act as molecular ruler by regulating the number of actin monomers that are allowedto assemble into a thin filament |
| What happens during contraction? | Myosin heads bend thus sliding the thin filaments over the thick filaments |
| How is energy provided? | by ATPase activity in the myosin head |
| Activated myosin attaches to actin for what purpose? | to initiate the power stroe and release the bound ADP which is then followed by binding of another ATP |
| What causes Rigor Mortis? | the absence of ATP prevents disociation of cross-bridges |
| What are the 5 steps of the Actinomyosin contractile cycle? | -ATP binds to myosin head causin detachment of head -hydrolysis of ATP to Pi and ADP energes head -head binds weakly to actin filament -Pi releases and tighter attachment to actin, power stroke=thin filament to center -ADP released =new cycle |
| Where is the calcium stored in the internal membrane? | Sarcoplasmic Reticulum (SR) |
| What is the contact between the nerve and muscle called? | Neuromuscular junction |
| The linking of the nerve impulse to the shortening of the sacromere is referred to as what? | Excitation-contracting coupling |
| Action potential in muscles is propagated into the cell interior by what? | Transverse (T) Tubules |
| T tubules terminate near where? | The Sarcoplasmic reticulum |
| The binding of Ca 2+ to Troponin causes what? | conformation changes, shifting tropomyosin and exposing the myosin binding state |
| What do Actin-binding proteins affect? | The localized assembly or disassembly of actin filaments |
| What are the 8 Actin-binding proteins? | -Nucleating proteins: template for adding actin -Monomer-sequestering proteins: bind to actin -End-blocking proteins: regulate length of actin fila.. -Monomer-polymerizing proteins: promote growth - |
| -Actin filament depolymerizing protein: bind actin-ADP -Cross linking proteins: alter 3D organization of actin -Filament severing proteins: shorten filaments -Membrane binding proteins: link contractile proteins | |
| Where are microvilli present wand what do they do? | on surface of epithelia. absorption of solutes, |
| How do cells lacking cilia and flagella move? | by crawling over substrate |
| Cultured cells crawl by creating a protrusion called? | Lamellipodium |
| What is a favored system for studying locomotion and why? | Keratocytes because their rapid gliding movement depends on the formation of very broad, thin lamellipodium |
| What is the role of Mysin 2? | to generate contractile forces needed to pull the rest of the cell behind the leading edge |
| The tip of the axon is called the? | Growth cone |
| What are 2 types of locomotor protrusions? | -Microspikes: point out the edge of lamellipodium -Filopodia: elongations that extend and retract during motile activity |
| Ectodermal cells elongate and form what and why? | Neural plate as microtubules become oriented parallel to the cells axis |
| Curvature of the neural tube causes what? | the outer edges to contact on another forming a ube which gives rise to the nervous system. |
| Chapter 15 | |
| What type of molecules transmit messages between cells? | Extracellular messenger molecules |
| What are the 3 types of intracellular signaling? | -Autocrine signaling (the cell has surface receptors that respond to messenger) -Paracrine (messenger molecules travel a short distance through extracellular space) -Endocrine (messenger molecules reach their target cells through bloodtream) |
| Some cell surface receptors generate what with what enzyme? | intracellular second messenger with an enzyme called effector |
| What are second messengers? | small substances that activate or inactivate specific proteins |
| What do signaling pathways consist of? | a series of proteins. |
| How is protein conformation usually altered? | Phosphorylation |
| What does Kinases and Phosphatases do? | Kinases add phosphate groups Phosphatases removes phosphate groups |
| What proteins receive a message to alter cell activity? | Target proteins |
| What is Signal transduction? | is a pathway that consists of Kinases and Phosphatases that change the conformations and acitivties of target proteins |
| What does Protein phosphorylation do? | changes protein behaviour in different ways |
| What are some of the wyas Protein Phosphorylation changes protein behaviour? | -can activate or inactivate an enzyme -can increase or decreas protein-proteins interactions -change the subcellular location of the proteins -can trigger protein degradation -phosphorylation patterns differ between cell type |
| What are the 5 different types of messengers? | -amino acids and their derivatives -gases, i.e NO and CO -Steroids -Eicosanoids (lipids derived from fatty acids) -Various peptides and proteins |
| What are the 5 types of receptors? | -G-protein coupled receptors (GPCRs) -Receptor protein-tyrosine kinases (RTKs) -Steroid hormone receptors -Specific receptors such as B-and T-cell receptors |
| GPCRs interact with which proteins? | G proteins |
| Ligand binding on the extracellular domain does what? | changes the intracellular domain |
| GDP is exchanged for what which activate what protein? | GTP on the G protein and activates the G protein |
| How does Desensitization occur? | by blocking active receptors from turning on the additional G proteins |
| What activates a GPCR via phosphorylation? | G protein-coupled receptor kinase (GRK) |
| What proteins compete with G proteins to bind to GCPRs? | Arrestins |
| What targets GPCRs and G proteins? | Bacterial Toxins such as cholera toxin |
| B Adrenergic Receptors stimulates what? | GAs to activate adenylate cyclase |
| What is Cyclic AMP? | it is a secondary messenger which is release into the cytoplasm after binding of a ligand |
| What do second messengers do to single extracellular ligands? | amplifies their response |
| What are Phosphoinositides (PI)? | derivatives of phosphotidylinositol |
| What does DAG do? | activates protein Kinase C, which phosphorylates serine and threonine residues on target proteins |
| Binding of IP3 opens what? | the calcium channels and allows Ca2+ ions to diffuse out |
| Glucagon and Epinepherine both do what? | these hormones stimulate glucose breakdown and inhibit its |
| cAMP is synthesized by what? | Adenylyl cyclase |
| a reaction cascade that leads glucose mobilization | |
| Phosphorylated transcription factors regulate what? | gene expression |
| AKAPs provide what of the signaling pathway? | subcellular localization |
| What is Rhodopsin? | a photosensitive protein for black-and-white vision that is also a GPCR |
| What are the 5 basic taste qualities that the taste receptors in the tongue transmits? | -sweet -salty -sour -bitter -savoury |
| Loss of function mutations results in what? | nonfunctional signal pathways |
| What does the Proteine-tyrosine kinases phosporylates? | tyrosine residues on the target proteins |
| What does Protein-tyrosine kinase do? | regulates cell growth, division, differentiation, survival and migration |
| Receptor protein-tyrosine kinases (RTKs) are what? | cell surface receptors of the protein-tyrosine kinase family |
| What does Phosphorylated tyrosines bind? | effector proteins that have SH2 domains and PTB domains |
| SH2 and PTB domains include what 4 things? | -adaptor proteins that bind other proteins -docking proteins that supply receptors with other tyrosine phosphorylation -Signaling enzymes that lead to change in cell -Transcription factors |
| What do GTPase-activating proteins (GAPs) do? | shorten the active time of Ras |
| What does Guanine nucleotide-exchange factors (GEFs) do? | stimulate the exchange of GDP for GTP |
| What do Guanine nucleotide-exchange dissociation inhibitors (GDIs) do? | inhibit the release of GDP |
| What is Ras? | a G protein embedded in the membrane by a lipid group |
| What is Ras-MAP kinase cascade? | a cascade of enzymes resulting in the activation of transcription factors |
| What do some scaffolds induce? | conformation change in signaling proteins, leading to activation or inhibition |
| What do scaffolds prevent? | proteins from participating in other pathways, resulting in higher specificity |
| What does Insulin do? | regulates blood glucose levels by increasing cell glucose uptake |
| What is the insulin receptor? | a protein-tyrosine kinase |
| What do Insulin receptor substrate proteins (IRSs) do? | bind proteins with SH2 domains to activate downstream signal molecules |
| What do activated IRS proteins activate? | major signaling pathways such as PI3K and Ras |
| What do active PI3K produce? | phosphorylated lipids that trigger activation of downstream proteins |
| What are the terminal effects of PI3K activation? | increased protein synthesis, glucose uptake and glycogen synthesis |
| How does PHB regulate glucose? | by GLUT4 transporters |
| Plants use what type of messengers? | Ca2+ and phosphoinositide messengers |
| *What do plants lack? | cyclic nucleotides and RTKs |
| Plants have protein kinases that phosphorylates what? | histidine residues and the product of the Etr1 gene encodes a gas ethylene that ripens, flowers and germinates plants |
| Why are calcium levels low in the cytosol? | because it is pumped out into the extracellular space and the membrane is highly impermeable to the ion |
| Calcium binds to what, which affects other proteins? | Calcium-binding proteins such as calmodulin |
| What happends during Store-operated calcium entry (SOCE)? | the depleted calcium levels trigger a response that lead to the opening of calcium channels |
| What are some stimuli that changes the response of Cytosolic calcium? | light, pressure, gravity and hormones |
| Signals form unrelated receptors do what in order to activate a common effector? | Converge |
| Identical signals do what in order to activate a variety of effectors? | Diverge |
| What is Crosstalk? | when signals are passed back and forth between pathways |
| What can block signals transmitted through the MAP kinase cascade? | cAMP |
| What is Nitric oxide (NO) is what? | an intracellular and extracellular messenger with a variety of functions |
| What is Apoptosis? | an ordered process involving cell shrinkage, loss of adhesion cells, dissection of chromatin and engulfment by phagocytosis |
| What are 4 Caspasses that cause Apoptotic changes? | -Protein kinases, some cause detachment of cells -Lamins, which line the nuclear envelope -Proteins of the cytoskeleton -Caspase activated DNase (CAD) |
| When is Apoptosis needed? | during embryonic developement to form structure, organs and tissues |
| What does Procaspases convert other Procaspases into? | caspases |
| Caspases activate what and why? | executioner caspases in order for apoptosis to happen |
| Chapter 16 | |
| Cancer results from what? | alterations in the DNA of somatic cells during the lifetime of the affected individual |
| What does metastasize? | establish secondary tumors |
| What is the difference, in relation to growth, between normal and malignant cells? | When there are no growth factors in the medium or when cells contact surronding cells: -normal cells stop growing but malignant cells continue to grow |
| What are the 3 similarities that different type of cancer cells share? | -Aberrant chromosome numbers -Fail to elicit Apoptosis -High metabolic requirements |
| How do mutagenic agents cause cancer? | altering the genome |
| What 2 things carry genes whose products interfere with cell growth regulation? | -DNA tumor viruses -RNA tumor viruses |
| What is tumorigenesis? | the development of a malignant tumor |
| How does tumorigenesis occur? | by a cumulative progression of genetic alterations |
| What are 2 things that cancer stem cells (CSC) can do? | -self replicate -produce progenitors that generate all of the cell types that make up tumors |
| Precancerous cells have what 3 properties? | -loss of certain growth controls -lack the capability to invade normal tissues -lack the ability to mestastasize to distant sites |
| What do Tumor-suppressive gene encode? | proteins that restrain cell growth. specific regions of chromosomes are deleted in cells of certain cancers |
| What do Oncogenes encode? | proteins that promote the loss of growth control and the conversion of a cell to a malignant state |
| A Proto-oncogene is what? | an oncogene that is an altered cellular gene |
| What do Proto-oncogenes encode? | proteins that function in a cells normal activities |
| Fa a cell to become malignant what is needed? | both alleles of a tumor suppressor geen must be lost and a proto-ongene must be converted into an oncogene |
| What 3 things can activate a conversion of proto-oncogenes into an oncogene? | -gene mutatation alters the properties of the product so it doesnt function as normal -the gene can be duplicated resulting in gene amplification and excess production -Chromosome rearangement that brings DNA sequen in close proxi of gene |
| What was the first tumor-suppressor gene to be discovered? | Retinoblastoma (RB) |
| How is RB developed? | requires both copies of RB to be altere or eliminated |
| What does protein RB (pRB) do? | regulates the G1 to S transition |
| What protein suppresses the formation of tumors and maitains genetic stability? | the p53 protein |
| The p53 protein acts as what? | transcription factor, activation the expression of a gene that inhibits the G1-S transition |
| Colon cancer is inherited when what is deleted? | the tumor suppressor gene called APC |
| Breast cancer is caused by mutations in what tumor suppressor gene? | BRCA |
| Simian Sarcoma virus contains what oncogene? | oncogene (sis) which is derived from a cellular gene which codes for the growth factor PDGF |
| Which oncogene directs the formation of an altered EGF receptor that stimulates the cell regardless of the presence of a growth factor? | oncogene (erbB) |
| What is Raf and what can it be converted into? | a serine-threonine kinase in the MAP kinase cascade. It can be converted into an oncogene by mutations that turn it into an enzyme that is always "on" |
| What does the Myc protein stimulate? | cells to reenter cell cycle from G0 stage |
| What do some oncogenes encode proteins to affect? | DNA methylation or histone modifications |
| Tumor cells are more reliant on what? | glycolysis compared to normal cells |
| The overexpression of Bcl-2 gene leads to what? | suppression of apoptosis allowing abnormal cells to proliferate into tumors |
| Protein producst from tumor suppressor genes and protooncogenes finely regukate what 4 pathways? | -Apoptosis or the sensitivity to apoptosis after insult -Proliferation and the response to external stimuli -Immortalization through the regulation of telomerase -Senescence where cells are metabolically active but not dividing |
| What does mismatch repair defects predispose cells to? | abnormally high mutation rates, which increases the risk of malignancy |
| Some miRNAs acto more like what? | oncogenes than tumor suppressors |
| S miRNAs are implicated in what? | tumor metastasis |
| What is used to diagnose cancer? | DNA microarrays |
| What are new strategies to target cancer cells? | -antibodies against tumor cells -inhibition of cancer-promoting proteins -preventing the growth of blood vessels that nourish the tumor |
| What is passive immunotherapy? | the strategy of using the patients own antibodies to respond to tumor cells |
| What is active immunotherapy? | get the patients own immune system to act against malignant cells |
| What is Angiogenesis? | the formation of new blood vessels |
| As tumors grow, what does it stimulate? | angiogenesis |
| What does an angiogenesis inhibitor do? | denies the tumor access to nutrients and oxygen needed to grow |
| Both viral adn cellular src genes encode for what? | protein kinase |
| How can cellular genes be converted to oncogenes? | by carcinogenic chemicals or by mutation sequences regulating their expression |
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